GC-MS analysis of switchgrass class II diTPS reaction products. Shown are individually scaled extracted or total ion chromatograms (EIC/TIC) and mass spectra of reaction products from in vivo and in vitro enzyme assays of the switchgrass class II diTPSs PvCPS15 and PvCPS14 (A), PvCPS11 (B), PvCPS8 (C), PvCPS3 (D and E), and PvCPS1 (F and G). Products of PvCPS15, PvCPS14, PvCPS11, and PvCPS8 were identified by comparison with theproducts of the known diTPSs ent-CPS (ZmAn2; Harris et al., 2005), ent-LPS (SdCPS2:W360A; Pelot et al., 2017b), and syn-CPS (OsCPS4; Xu et al., 2004). The PvCPS3 and PvCPS1 reaction products were identified by GC-MS and NMR analysis as (+)-labda-8,13E-dienyl diphosphate (E) and ent-neo-cis-trans-clerodienyl diphosphate (G), respectively. Details on NMR structural validation and the proposed absolute stereochemistries are given in Supplemental Figures S2 to S4. Numbered peaks are as follows: 1, ent-copalol (i.e. dephosphorylated ent-copalyl diphosphate; CPP); 2, unidentified diterpene; 5, ent-8β-labda-13E-en-8,15-diol (i.e. dephosphorylated ent-labda-13-en-8-ol diphosphate; LPP); 6, ent-8α-labda-13E-en-8,15-diol; 9, syn-copalol (i.e. dephosphorylated syn-CPP); 10, unidentified diterpene; 11, (+)-labda-8,13E-dien-15-ol (i.e. dephosphorylated [+]-labda-8,13E-dienyl diphosphate; 8,13-CPP); 12, ent-neo-cis-trans-kolavenol (i.e. dephosphorylated ent-neo-cis-trans-clerodienyl diphosphate; CT-CLPP); 13, unidentified diterpene.